Four families with heritable forms of premature ovarian failure are being investigated. At the present time no previously identified etiology of premature ovarian failure has been found in these women. Prenatal galactose treatment during the first half of pregnancy decreases oocyte number in the rat. This suggests that primordial germ cell proliferation or migration, or oogonial proliferation are adversely effected by galactose. This rodent system represents a useful model for exploration of the mechanism of premature ovarian failure observed in women with galactosemia.